1. Field of the Invention
The present invention is directed to an arrangement for identifying the position of a movable body with ultrasound, comprising a main transducer that serves as a transmitter and a receiver for ultrasonic pulses, a reflector attached to the body and having a reflecting front side and rear side which reflects an ultrasonic pulse transmitted from the main transducer from the front side back in the direction of the main transducer, a measuring device to which the main transducer is connected and which identifies a principal transit time per ultrasonic pulse which requires a long principal distance between the main transducer and reflector from the main transducer to the reflector and back, and which identifies a position value therefrom that represents the position of the reflector relative to a reference position having a reference distance from the main transducer.
2. Description of the Prior Art
In known arrangements of the type set forth above, the principal distance between the main transducer and the reflector that is attached to a body is identified as a position value by measuring the transit time of an ultrasonic pulse in a medium between the main transducer and the reflector, referred to as the principal transit time hereinbelow, and being identified according to the following equation EQU L.sub.1 =1/2.multidot.t.sub.1 .multidot.v(.theta.) (1)
where t.sub.1 is the principal transit time of the ultrasonic pulse, v(.theta.) denotes the propagation speed of the ultrasonic pulse in the medium, L.sub.1 denotes the principal distance and .theta. denotes the temperature.
Since the propagation speed is highly dependent on the temperature of the medium, the temperature of the medium must be additionally measured in order to be able to carry out a temperature correction. A temperature sensor comprising a following, involved measuring electronic circuit is used for this purpose.
Furthermore, the propagation speed is a specific function of the medium, with a consequence that the measuring electronic circuit must evaluate a characteristic or an equation for the specific propagation speed for each medium. In the known arrangements, the measuring electronic circuits employed must therefore be adapted to each medium in a technically-involved manner.